A181758 Greatest prime closest to n^3.

2, 7, 29, 67, 127, 211, 347, 509, 727, 997, 1327, 1733, 2203, 2741, 3373, 4099, 4909, 5827, 6857, 7993, 9257, 10651, 12163, 13829, 15629, 17579, 19681, 21961, 24391, 26993, 29789, 32771, 35933, 39301, 42863, 46663, 50651, 54869, 59333, 63997, 68917, 74093, 79493, 85193, 91127, 97327, 103813, 110597, 117643, 125003

Offset

1,1

Links

David A. Corneth, Table of n, a(n) for n = 1..10000

Example

29 is the greatest prime closest to 3^3 = 27.

Mathematica

f3[n_]:=Module[{n3=n^3, np1, np2}, np1=NextPrime[n3, -1]; np2=NextPrime[n3]; If[(n3-np1)<(np2-n3), np1, np2]];
Table[f3[i], {i, 50}]

Prog

(PARI) a(n) = {if(n == 1, return(1)); my(n3 = n^3, gp = nextprime(n^3), lp = precprime(n^3)); if(n3 - lp < gp - n3, return(lp) , return(gp) ) } \\ David A. Corneth, May 25 2021

Crossrefs

Cf. A113426.

Sequence in context: A359633 A339868 A386166 * A285790 A083016 A062064

Adjacent sequences: A181755 A181756 A181757 * A181759 A181760 A181761

Keyword

nonn

Author

Harvey P. Dale

Status

approved